Composition for structural adhesive

ABSTRACT

The invention relates to a composition for a structural acrylic adhesive that comprises an adhesion promoter including a phosphate ester and a high molecular-weight polyamine as a polymerisation accelerator.

RELATED APPLICATIONS

This application is a national stage application (under 35 U.S.C. § 371)of PCT/EP2009/053332, filed Mar. 20, 2009, which claims benefit ofFrench application 08/01553, filed Mar. 21, 2008.

FIELD OF THE INVENTION

The present invention relates to the field of acrylic structuraladhesives (based on acrylate or on methacrylate) and to the usesthereof.

BACKGROUND OF THE INVENTION

Structural adhesives are a good alternative to other mechanicaltechniques for binding two materials together, such as metals orplastics. This is because the force distribution is better with bondingthan when alternative techniques such as riveting or welding are used.In addition, the use of bonding often makes it possible to work morerapidly, and also has the advantage of providing better insulationagainst external elements (dust, moisture) than the mechanicaltechnologies.

Structural adhesives are formed from two components: a compositioncontaining the curing agent (based on acrylate or on methacrylate) and acatalyst for curing and setting the adhesive. These two components arestored in two different compartments and are mixed at the time ofapplication of the adhesive. This catalyst is a free-radicalpolymerization initiator, in particular based on peroxide, and is wellknown in the art.

The compositions containing the curing agent also contain otherelements, such as a cure accelerator, a rheology modifier or an adhesionpromoter.

The cure accelerator serves to promote curing and hardening of theadhesive when the catalyst is added. The use of tertiary amines,preferably aromatic tertiary amines, such as dimethyl-para-toluidine(DMPT), and/or 2,2′-(p-tolylimino)diethanol or dimethylaniline (DMA), isknown in the art.

These cure accelerators make it possible to obtain a high degree ofcuring of the adhesive and to improve its mechanical performance levelsand its strength in a difficult environment.

Such tertiary amines are in particular described in U.S. Pat. No.4,223,115 and EP 894 119.

SUMMARY OF THE INVENTION

However, these amines have certain disadvantages, in particular withregard to the curing parameters (gelation, exothermicity) which makethem unsuitable for certain industrial applications.

In the context of the present invention, the inventors have substitutedthis category of tertiary amine with another category ofhigh-molecular-weight tertiary amine which is less toxic, as describedin WO 03/086327, which makes it possible to preserve the mechanicalproperties and the strength properties over time by virtue of a degreeof curing which is just as high.

Thus, the amines used in the context of the invention are not toxic, canbe used at a lower dosage than the prior art amines, and reactcompletely with the free-radical polymerization initiator. Moreover,surprisingly, such amines improve the rapidity of gelation of adhesives,compared with the prior art amines. This makes it possible to usestructural adhesives in new applications, as described hereinafter.

Document WO 98/34980 describes the use of amines as can be used in thecontext of the present invention, as a marker for curing owing to thechange in color of the amine during the curing. The compositionsdescribed in this document thus also comprise a reducing agent forinitiating curing by generating free radicals after interaction with anoxidizing agent.

Document JP 2007 169560 describes the use of amines as usable in thecontext of the present invention, for coloring during curing, apolymerization initiator being used, moreover.

Thus, the invention relates to a composition that can be used in astructural adhesive, said structural adhesive being formed from saidcomposition and from a catalyst comprising a radical polymerizationinitiator of peroxide type, said composition comprising:

-   -   (a) at least one methacrylate ester monomer,    -   (b) a phosphate-ester-based adhesion promoter,    -   (c) a cure accelerator comprising a tertiary amine of formula I:

-   -   in which:        -   the R3 group is a resonance electron-donating group            comprising at least one aromatic group which is capable of            forming, with the radical:

-   -   and in combination with said radical polymerization initiator, a        conjugated system exhibiting an absorption in the visible field        of the electromagnetic spectrum, so as to generate a coloration        of said polymer or of said cement during the reaction for        polymerizing said monomer,        -   the R1 and R2 groups are respectively and independently:            -   linear or branched C₁ to C₁₆, preferably C₁ to C₅,                groups,            -   C₅ to C₃₀, preferably C₅ to C₁₀ aryl or arylalkyl                groups,            -   C₂ to C₁₅, preferably C₂ to C₅, alkylidene groups.

DETAILED DESCRIPTION OF THE INVENTION

In one preferred embodiment, said R3 group comprises at least onetertiary amine linked to an aromatic group, which makes it possible inparticular to improve the activation. Thus, the composition according tothe invention contains tertiary polyamines, the tertiary amine groupsbeing borne by aromatic groups. This particular architecture makes itpossible to color the adhesive during the curing phase.

In one preferred embodiment, the R3 group comprises at least twotertiary amines linked to two distinct aromatic groups, and is inparticular of the form:

-   -   in which:        -   X is chosen from: CH and N, and        -   R4, R5, R6 and R7 are chosen from:            -   linear or branched C₁ to C₁₆, preferably C₁ to C₅, alkyl                groups,            -   C₅ to C₃₀, preferably C₅ to C₅, aryl or arylalkyl                groups,            -   C₂ to C₁₅, preferably C₂ to C₅, alkylidene groups.

Use is particularly preferably made, as cure accelerator in the contextof the invention, of a polyamine corresponding to the formula:

This tertiary triamine is 4,4′,4″-methylidynetris(N,N-dimethylaniline).It is also referred to as “leuco crystal violet”, “leuco” or “LCV”. Thesymmetry of the molecule and the presence of three possible active sitesfor activating the radical polymerization initiator make this polyamineparticularly preferred for the use of the invention.

Other amines corresponding to formula (I) are described in WO 03/086327.These high-molecular-weight polyamines can also be for producing acomposition according to the invention. It is also possible to mixseveral polyamines in a composition according to the invention, or toadd other cure activators, although, in one particular embodiment, thecomposition does not comprise any cure activators other than the aminesof formula (I).

It is possible to use an activator of formula (I) which is a tertiarydiamine of formula (I) in which the R3 group is of the form:

where

-   -   X′ is chosen from: CH₂, O, O—C₆H₄—O, N—H and N—R, and    -   R8, R9 and R are respectively and independently:        -   linear or branched C₁ to C₁₆, preferably C₁ to C₅, alkyl            groups,        -   C₅ to C₃₀, preferably C₅ to C₁₀, aryl or arylalkyl groups,        -   C₂ to C₁₅, preferably C₂ to C₅, alkylidene groups.

The activator of formula (I) may also be chosen such that R3 is of theform:

-   -   X₁ and X₂ being chosen from: N and CH,    -   R10 to R15 being independently:        -   linear or branched C₁ to C₁₆, preferably C₁ to C₅, alkyl            groups,        -   C₅ to C₃₀, preferably C₅ to C₁₀, aryl or arylalkyl groups,        -   C₂ to C₁₅, preferably C₂ to C₅, alkylidene groups.

The cure accelerator is added in an amount of between 0.1% and 2% byweight in the composition, preferably between 0.2% and 1.5% by weight.

In the context of the composition according to the invention, thephosphate-ester-based adhesion promoter is preferably methacrylated. Inparticular, a phosphate-ester-based adhesion promoter which is the2-hydroxyethyl methacrylate phosphate ester is used. It may inparticular be obtained under the name Genorad 40 (Rahn AG, Zurich,Switzerland). Such adhesion promoters are well-known in the art, and arein particular described in U.S. Pat. No. 4,223,115. Mention may thus bemade of 2-methacryloyloxyethyl phosphate, bis(2-methacryloyl-oxyethylphosphate), 2-acryloyloxyethyl phosphate, bis(2-acryloyloxyethylphosphate), methyl-(2-meth-acryloyloxyethyl phosphate),ethyl-(2-methacryloyl-oxyethyl phosphate), a mixture of 2-hydroxyethylmethacrylate monophosphate and diphosphate esters (in particular theproduct known under the name T-Mulz 1228 (Harcros Organics, Kansas City,US)) and related compounds or derivatives. Between 1% and 6% by weightof this adhesion promoter is added, preferably between 2% and 4%.

The combined use of an adhesion promoter and of a high-molecular-weighttertiary polyamine according to the invention in fact makes it possibleto accelerate the gelation compared with the use of the same adhesionpromoter and of a low-molecular-weight amine of the prior art.

In one preferred embodiment, the ester monomer (a) is a methacrylatemonomer. A methacrylate monomer in which the alcohol part has a shortlinear chain (i.e. having one or two carbon atoms) is preferably chosen.Thus, the preferred monomers according to the invention are methylmethacrylate and ethyl methacrylate.

In another embodiment, the alcohol part has at least one ring, which maybe substituted or unsubstituted. Thus, in this embodiment, the monomerscan in particular be chosen from tetrahydrofurfuryl methacrylate,phenoxyethyl methacrylate, isobornyl methacrylate, glycidyl ethermethacrylate, benzyl methacrylate, cyclohexyl methacrylate,trimethyl-cyclohexyl methacrylate and hydroxyethyl methacrylate.

Mixtures of these esters can also be used. The percentage by weight ofmethacrylate ester in the composition is preferably between 20% and 80%,more preferably between 30% and 65%, even more preferably from 39% to58%, i.e. approximately in the region of 50%.

As mentioned above, the use of cure accelerators in the compositionsaccording to the invention makes it possible to accelerate the gelationof the adhesives using such compositions, and to modify theexothermicity peak. It may, however, be advantageous to control thisgelation, and to delay it. This can be carried out by adding, to acomposition according to the invention, an amine (d) chosen from thegroup of substituted or unsubstituted anilines, toluidines and phenols.Preference is in particular given to para-toluidines of formula:

The R′ and R″ groups that can be used are in particular C₁ to C₆ alkylgroups, OH groups, OC_(n)H_(2n-1) groups with n less than or equal to 4,OOCCH₃ groups or the like, or OR groups in which R is a C₁ to C₆ alkyl.Particularly suitable amines (d) are especiallyN,N-bis(2-hydroxyethyl)-p-toluidine, N-methyl-N-hydroxyethyl-p-toluidineor N,N-bis(2-hydroxyethyl)-3-methylaniline, or2,4,6-tri(dimethylaminomethyl)phenol. The amount of these amines in thecomposition is between 0.5% and 3% by weight.

The composition may also contain a metallic acrylate or methacrylatemonomer (e) (metallic salt (or comparable) of acrylic or methacrylicacid), which is in particular zinc-based. The presence of this compoundin the composition makes it possible in particular to improve themechanical performance levels of the adhesive, and also to adjust thegel and/or exothermicity times. As compound (e), use may in particularbe made of zinc diacrylate, zinc dimethacrylate, zinc monomethacrylate,iron diacrylate, iron dimethacrylate, iron monomethacrylate, calciumdiacrylate, calcium dimethacrylate, calcium monomethacrylate, magnesiumdiacrylate, magnesium dimethacrylate and magnesium monomethacrylatemonomers. The amount of this salt in the composition is between 0.5% and3% by weight.

It is preferable for the composition to also contain at least oneelastomer (f). If required, it is functionalized (having a double bondat its ends, in particular methacrylate functions so as to improve thebonds with the monomers). In certain cases, a liquid elastomer ischosen. At least one functionalized elastomer, alone or as a mixturewith at least one non-functionalized elastomer, is preferably used.

When the composition contains one or more elastomeric block copolymers(see below), the elastomer (f) is chosen such that it is compatible insolution with the block copolymers used. In particular, it is chosen insuch a way that its Hildebrand solubility parameter is compatible withthe Hildebrand solubility parameters of the block copolymers used. Inparticular, it is chosen in such a way that its value does not differ bymore than 10% from the average of the values of the Hildebrandsolubility parameters of the block copolymers used (for example, 8.3(cal.cm⁻³)^(1/2) for the SIBS MD6455). The Hildebrand solubilityparameter is well known and is calculated by the square root of thecohesive energy density of the compound. The Hildebrand solubilityparameter is directly related to the dispersion forces (Van der Waalsforces) which are exerted between the molecules of a chemical substance.In particular, the Hildebrand solubility parameter (expressed ascal^(1/2) cm^(−3/2)) of the elastomer (h) is between 8 and 9 (between 16and 19 when the solubility parameters are expressed as MPa^(1/2)). Thusit is preferred to use elastomers of the polybutadiene homo-polymer type(the polybutadiene then being preferably chosen to be liquid andfunctionalized), or polyisoprene homopolymer type. Polychloroprene(Neoprene AD10, DuPont, USA) can also be used. Butadiene-acrylonitrilecopolymer elastomers, which are in particular functionalized, can alsobe used. The functionalities are borne by the end chains and thefunctional groups that can be used are carboxyl (COOH), amine (NH orNH₂), vinyl methacrylate or epoxy groups.

It is thus possible to use a functionalized poly-butadiene such asHypro™ VTB 2000×168 (vinyl end groups), alone or as a blend with apolychloroprene or a nonfunctionalized polybutadiene such as Hypro™ CTB2000×162 (carboxyl end groups) (Emerald Performance Materials (EPM),Cuyahoga Falls, Ohio, USA). It is also possible to use Hypro™ VTBNX orCTBNX (butadiene-acrylonitrile copolymers) having, respectively,carboxyl and vinyl functionalities, and more particularly Hypro™ VTBNX1300×43 or 1300×33.

This elastomer (f) is preferably present in an amount of between 4% and30% by weight in the composition according to the invention, preferablybetween 6% and 15%, more preferably between 8% and 12%. A smaller amountof elastomer is used when the composition contains one or more blockcopolymers (see below).

In one particular embodiment, the composition also contains anelastomeric block copolymer containing styrene and at least one secondmonomer (g). Said second monomer of the elastomeric block copolymer (g)is advantageously chosen from isoprene, butadiene and ethylene. Inparticular, the block copolymer (g) is chosen from a block copolymercontaining styrene and isoprene, an elastomeric block copolymercontaining styrene and butadiene or ethylene, and blends thereof.

The composition according to the invention may also contain a blend ofvarious block copolymers. Thus, in another embodiment, it comprises astyrene-isoprene-styrene (SIS) block copolymer (g) and at least oneblock copolymer containing styrene and butadiene or ethylene (h).

When it contains butadiene, this block copolymer (h) can be astyrene-butadiene-styrene (SBS) or a styrene-isoprene-butadiene-styrene(SIBS) copolymer such as Kraton MD6455 (from the company KratonPolymers) described by Dr Donn DuBois et al., at the Adhesives &Sealants Council Meeting, Louisville, Ky., 9-12 Oct. 2005.

When it contains ethylene, this block copolymer (h) can be a SEBS(styrene-ethylene/butylene-styrene copolymer) or a SEPS(styrene-ethylene/propylene-styrene copolymer). These compounds areavailable in the Kraton G range (Kraton Polymers).

In the preferred embodiment of the invention, the block copolymer (h)contains butadiene.

Preferably, the styrene is present in a proportion of between 15% and50%, more preferably between 22% and 40%, even more preferablyapproximately 28-33% by weight of the SBS copolymer. It is present in aproportion of between 12% and 24%, more preferably at approximately18-19% by weight in the SIS or SIBS copolymers.

Preferably, the composition contains a blend of an SIS and of an SIBS ina proportion ranging from 4:1 (by weight in the composition) to 1.5:1.The preferred proportion of SIS relative to the SIBS is approximately3:1 or 3.3:1. However, it is also possible to use a blend of SIS and ofSBS in the same relative proportions as the SIS/SIBS blend. A blend ofSIS, SIBS and SBS can also be used. Another block copolymer can also beadded to one of these blends.

The SIS, SBS or SIBS block copolymers that can be used according to theinvention are well known to those skilled in the art. They are inparticular produced by the company Kraton Polymers (Houston, Tex., USA).Thus, the Kraton D1160 SIS described in US 20050238603 or Kraton K1161,the Kraton D1102 SBS described in U.S. Pat. No. 5,106,917 and the KratonMD6455 or Kraton MD 6460 SIBS can be used.

Those skilled in the art know how to select the SIS, SIBS or SBS blockcopolymers that can be used in the composition according to theinvention, from those which exist, according in particular to theirability to dissolve in the monomers used, or to their tensile mechanicalstrength.

Preferably, the composition according to the invention comprises between5% and 30% by weight, preferably between 12% and 25%, and morepreferably between 15% and 25%, of the elastomeric block copolymer(s).

In one particular embodiment, the composition according to the inventioncontains an elastomeric block copolymer containing styrene and isopreneand at least one elastomeric block copolymer containing styrene andbutadiene, i.e. an SIS/SIBS blend, an SIS/SBS blend, or an SIS/SIBS/SBSblend.

In another embodiment, the composition according to the inventioncontains a single elastomeric block copolymer, containing styrene andisoprene, i.e. an SIS.

In another embodiment, the composition according to the inventioncontains a single elastomeric block copolymer, containing styrene andbutadiene, chosen from an SIBS or an SBS.

If the composition contains one or more block copolymers, the relativeproportions of the blend of block copolymers ((g) and/or (h)) and of theelastomer (f) are between 4:1 and 0.5:1 by weight in the composition,preferably approximately 2:1. However, it is also possible to haverelative proportions of the order of approximately 0.5:1.

The composition according to the invention may also contain elastomericpolymeric particles (i). These particles are called “core-shell”, arewell known to those skilled in the art, and are formed from a “hard”thermoplastic shell, preferably based on poly(methyl methacrylate)(PMMA), and from an elastomeric core generally based on butadiene, oftencopolymerized with styrene, or acrylic-based. In the use of theinvention, mention may especially be made ofacrylonitrile-butadiene-styrene (ABS), methacrylate-butadiene-styrene(MBS), methacrylate-acrylonitrile-butadiene-styrene (MABS) andmethacrylate-acrylonitrile polymers, and blends thereof.

These particles contain a crosslinked elastomeric core surrounded by athermoplastic shell, which is often a methyl methacrylate polymer(PMMA). U.S. Pat. Nos. 3,985,703, U.S. Pat. Nos. 4,304,709, U.S. Pat.Nos. 6,433,091, EP 1256615 or U.S. Pat. No. 6,869,497 describe inparticular such particles, which are thus well known to those skilled inthe art.

In particular, impact-modifying particles are preferred, particularlyMBS impact modifiers. In one preferred embodiment, these MBSs have aslight crosslinking of the polymer forming the core. In addition, theseMBSs, in addition to their impact resistance, also preferably have ashock-induced crack resistance.

Core-shell polymers are available from many companies. Mention may thusbe made of GE Plastics or Arkema (Paris, France). The preferredparticles are in particular of the Clearstrength C301, C303H, C223,C350, C351, E920 or C859 type from Arkema, the C301 and C303H MBSs beingpreferred. It is also possible to use Durastrength D300 or D340 fromArkema, having an acrylic core surrounded by a PMMA shell. Likewise, itis also possible to use the MBSs developed by Rohm & Haas (Philadelphia,Pa., United States), in particular Paraloid™ BTA 753.

These particles (i) may be used by themselves or as a mixture. Thus, inone particular embodiment of the invention, a mixture of MBS particles(in particular C303H or C301) and of particles having a PMMA shell andan acrylonitrile core (in particular D340 particles) is used.

Preferably, these particles (i) are present in the composition in anamount of between 2% and 20% by weight of the composition, preferablybetween 5% and 15% by weight.

In one particular embodiment, the composition also contains at least oneacrylic ester monomer (j) in which the alcohol part has a linear chainof at least 6 carbon atoms (a long-chain monomer). Thus, it is preferredto use lauryl methacrylate, 2-ethylhexyl methacrylate, 2-ethylhexylacrylate, esters based on polyethylene glycol, or mixtures of theseesters. It is preferable for the composition to contain at most 10%,more preferably at most 8%, or even at most 5% by weight in total ofthese long-chain acrylic monomers. In one particular embodiment, thecomposition comprises a mixture of two long-chain acrylic estermonomers. Preferably, when the composition contains only a singleacrylic ester monomer (h), it is preferable for it to be present in anamount of less than or equal to 8% by weight, although it is acceptablefor there to be an amount thereof of between 8% and 10% when thecomposition contains a mixture of these esters (j). In this case, it ispreferred for each to be present at no more than 5%.

The composition may also contain other monomers such as acrylonitrile,methacrylonitrile or styrene.

The composition according to the invention may also contain an acidmonomer such as an acid monomer that can be polymerized by freeradicals, known in the art, of the unsaturated carboxylic acid, maleicacid, crotonic acid, isophthalic acid and fumaric acid type. It is alsopossible to add isobornyl acrylate (IBXA), 2-hydroxyethyl methacrylate(HEMA), 2-hydroxypropyl methacrylate (HPMA), 2-(perfluorooctyl)ethylacrylate (POA), tetrahydrofurfuryl acrylate (THFA) orisobutoxy-methylacrylamide (IBMA). Mixtures of these compounds, inparticular a mixture of HEMA and HPMA, may be added. Methacrylic acid oracrylic acid or HEMA is preferred. Between 2% and 10% of this compound,preferably between 3% and 7%, are added.

The composition according to the invention may also contain, in itspreferred embodiments, at least one additional compound such as arheology modifier. The rheology modifier serves to provide goodviscosity of the composition according to the invention, so that it canbe easily applied to the surfaces to be bonded. Polyamides such asDisparlon 6500 (Kusumoto Chemicals Ltd, Japan) or pulverulent elementsbased on silica or the like (untreated fumed silica or pyrogenic silica)may be used.

The composition may also contain metal ions, and also other compoundssuch as saccharin (a sweetener authorized in Europe under number E-954,also called 1,1-dioxo-1,2-benzothiazol-3-one) or its derivatives (see WO87/000536), and/or 1′1-acetyl-2-phenylhydrazine (between 0.1% and 5% byweight).

Other components such as mineral fillers (TiO₂, CaCO₃, Al₂O₃, zincphosphate), ultraviolet stabilizers (such as 2-hydroxyphenyltriazine,Tinuvin 400 from Ciba-Geigy) and wax may also be added to thecomposition according to the invention. Free-radical polymerizationinhibitors such as BHT, or benzoquinones such as naphthoquinone,hydroquinone or ethylhydroquinone may also be added in order to increasethe lifetime of the composition.

In another embodiment, the invention relates to a composition comprisinga methacrylate ester monomer, a cure accelerator/initiator comprising atertiary amine of formula (I) as defined above, and saccharin (or asaccharin derivative). In this embodiment, it may be advantageous forthis composition to contain an acid monomer, in particular HEMA. In thisembodiment, the presence of the adhesion promoter (b) is preferred, butis not obligatory. In this embodiment, the composition may also containthe components (d) to (j) as described above, and also the othercomponents mentioned above.

As mentioned above, the structural adhesives are formed from twocomponents which are a composition according to the invention and acatalyst for curing and setting the adhesive. These two components arestored in two different compartments and are mixed at the time ofapplication of the adhesive.

As mentioned, a catalyst which is a free-radical polymerizationinitiator, and which is in particular peroxide-based, is chosen. Suchcatalysts are well known in the art. Benzoyl peroxide,tert-butylperoxybenzoate and cumene hydroperoxide may in particular bechosen. It is preferred when the catalyst contains between 5% and 40% byweight of peroxide, in particular approximately 20% by weight ofperoxide. A paste containing approximately 20% of benzoyl peroxide is inparticular used. This catalyst is in particular contained in aplasticizer such as diisobutyl phthalate or benzyl phthalate.

The catalyst is used in a ratio of from 1:1 to 1:30 (by volume),preferably from 1:5 to 1:30, even more preferably approximately 1:10,relative to the second component, which is the composition according tothe invention.

The invention thus relates to the combined use of a compositionaccording to the invention and of a catalyst comprising a free-radicalpolymerization initiator of peroxide type in a method for adhesivelybonding one material to a second material, and in particular when atleast one of the materials is metallic.

The use of a composition according to the invention and of a catalysttherefore makes it possible to bond metals, plastics and composites to acomposite and thus can be applied in particular in the field of silo,boat or truck trailer construction. It can also be used in theautomotive construction field or the railroad field.

Thus, the composition enables a material to be adhesively bonded toanother material, one or the other material being in particular a metal,a plastic, wood or a composite. The composition may therefore be used inone or other of the following applications: metal/metal,metal/composite, metal/plastic, metal/wood, wood/plastic,wood/composite, wood/wood, plastic/composite, plastic/plastic orcomposite/composite adhesion.

The composition according to the invention is also particularlyadvantageous when a material has to be bonded to a composite or a metal.

The flexible methacrylate structural adhesives having high mechanicalperformance obtained with the composition according to the invention areresilient and resistant to shocks and vibrations. They make it possibleto produce adhesive joints between materials of the same or differentchemical nature, for example: concrete, wood, ceramics, glass, ferrites,aluminum, anodized aluminum, steel, galvanized steel, stainless steel,painted metals, steel, copper, zinc, ABS, PVC, polyester, acrylics,polystyrene, gel-coat polyester or epoxides, composites,glass-fiber-reinforced composites, laminates, honeycomb structures andany painted or lacquered material. The structural adhesives obtainedwith the composition according to the invention are particularlyadvantageous for bonding galvanized steel or electrogalvanized steel.

They can also fill large gaps between substrates of different andvariable thickness, roughness or flatness, with better stressdistribution.

The flexibility of this composition thus makes it possible to take upthe forces of differential dilations between the substrates over longlengths of several meters, reducing and eliminating the geometricalfaults (angle, roughness, flatness).

The applications and activity sectors involved comprise in particular:

Bonding of reinforcements, rails, frame structures, beams, stiffeners,panels, partitions, fasteners, supports, body components, reinforcingbrackets, inserts, cylindrical and conical components, hinges, frames,etc.; bonding with lamination take-up on partitions, bonding withfilling requiring high mechanical strength;

In particular bonding of any bonded structural or mechanical componentfrom the following fields of construction: shipbuilding, automotive,railroad (and infrastructure), aeronautical, aerospace, electronic,electromechanical and domestic electrical equipment, militarystructures, shop signs, traffic (and advertising) signs, urbanfurniture, exterior joinery (windows, picture windows, French doors,entry doors and garage doors), wind machines, containers, engineeringstructures and infrastructures (in particular suspension bridges,offshore oil platforms and aircraft hangers), construction andfastening, curtain walling and solar panels.

When the adhesive produced with a composition according to the inventionexhibits a rapid gelation, this makes it possible to solve the followingproblems:

-   -   magnet bonding in the manufacture of loudspeakers: rapid        progression to gel time on the assembly line in fact makes it        possible to immobilize or fix the parts rapidly without them        having the time to slide on one another with a high production        rate enabling a bonding procedure to be carried out every 2        minutes instead of every 4 minutes.    -   Magnet bonding (manufacture of windshield-wiper motors, small        motors), assembly of electronic components.    -   Bonding of rearview mirror inserts on a windshield: metal and        plastic on laminated glass (for the repair, the operator does        not have to hold the insert on the glass for more than one to        two minutes).    -   Bonding of inserts vertically on supports made of metals and        composites: stainless steel male insert on a square plate 32×32        mm onto which a tapped bushing is welded: it involves a male        insert with a perforated plate 38 mm in diameter, onto which an        M6 threaded stud 25 mm in length is welded (see in particular        the Bighead® inserts (Bighead Bonding Fastener, Bournemouth,        GB)). Rapid bonding with a gel time is necessary in order to        avoid the perforated insert sliding on the vertical support. The        adhesive rapidly plays its role of rivet in the perforations of        the insert.    -   Rapid positioning on high production rate assembly lines and on        many materials.    -   Positioning and bonding of packing pieces.    -   Rapid assembly on an assembly line with gaps that may be large,        up to 5 mm, and on a multitude of materials: aluminum, steel,        galvanized steel, stainless steel, electro-galvanized steel,        bronze, lacquered steel, thermoplastics, glass, and composites.    -   Bonding on wood and plywood, making it possible to prevent the        wood absorbing the monomers too rapidly.

EXAMPLES

The examples below illustrate the invention without restricting thescope thereof.

Example 1 Raw Materials Used and Methodology

The following components were used:

Composition

-   -   methacrylate ester monomer (a): methyl methacrylate        (MMA)/isobornyl methacrylate/hydroxyethyl methacrylate    -   functionalized liquid elastomer (f): HYPRO™ VTB 2000×168 (EPM,        USA)    -   acid monomer: methacrylic acid (MAA)    -   adhesion promoter (b): phosphate methacrylate Genorad 40 (Rahn        AG)    -   cure accelerator (c):        4,4′,4″-methylidyne-tris(N,N-dimethylaniline) (LCV)    -   cure accelerator (control): N,N-dimethylaniline (DMA), or        dimethyl-para-toluidine (DMPT)    -   toluidine (d): N,N-bis(2-hydroxyethyl)-p-toluidine (PTE)    -   zinc dimethacrylate (e): SR 708 (Sartomer)    -   fillers: metal ions, rheology modifiers, pulverulents    -   SIS copolymer (g): Kraton D1160 (Kraton Polymers)    -   SIBS copolymer (h): Kraton MD6455 (Kraton Polymers) 25    -   rheology modifier: Disparlon 6500 (Kusumoto Chemicals)    -   elastomeric polymeric particles (i): Clearstrength C303H        (Arkema).        Catalyst    -   benzoyl peroxide at 20%.

Ratio of composition:catalyst mixture=10:1.

The tensile shear strength (SS) was measured according to the ISO 4587standard. Briefly, 2024T3 aluminum test pieces measuring 100×25×1.6 mm(L×W×T) were used. Two test pieces were bonded to each other, theoverlap area being 25×12 mm (300 mm²), with an adhesive joint thicknessof approximately 200 to 400 μm. The force needed to break the adhesivejoint was then measured by pulling on the two test pieces.

In order to be industrially useable, it is preferable for it to bepossible to handle the adhesive for several minutes (which correspondsto the gel time) and for the adhesive to cure rapidly after gelation. Itis preferable for the maximum exothermicity time to be close to the geltime so that the user can rapidly handle his or her parts.

The gel time and the maximum exothermicity peak were also measured.

Example 2 Use of a High-Molecular-Weight Polyamine

The following compositions were analyzed:

Components A1 A2 A3 A4 A5 Methyl 28.5  28.5  28.5  27.0  29.0 methacrylate VTB 2000x168 28.0  28.0  28.0  28.0  28.0  Isobornyl 5.55.5 5.5 5.5 5.5 methacrylate Hydroxyethyl 6.0 6.0 6.0 6.0 6.0methacrylate Methacrylic 4.0 4.0 4.0 4.0 4.0 acid Genorad 40 3.0 3.0 3.03.0 3.0 SR 708 — — — 1.5 — DMA 1.0 — — — — DMPT 1.0 — PTE — LCV — — 1.01.0 0.5 Fillers 24.0  24.0  24.0  24.0  24.0  Gel time 9 min 4 min 54 s54 s 2 min (on 20 gr) 25 s 10 s 33 s Maximum 15 min 7 min 8 min 2 min 71min exothermicity 40 s 36 s 28 s 36 s 48 s 108° C. 116° C. 119° C. 109.5° C. 89° C. Shear strength 16.7 15.7 15.3 17.9 15.8 MPa MPa MPa MPa MPaFracture 100% 100% 100% 100% 100% surfaces cohe- cohe- cohe- cohe- cohe-sive sive sive sive sive Formulation A1: uses an amine as described inthe prior art (control). Formulation A2: uses an amine as described inthe prior art (control). Formulation A3: the gel time is very rapid, theexothermicity peak being more distant. Formulation A4: use of SR 708from Sartomer in combination with LVC: this metallic dimethacrylatemonomer accelerates the curing rate (exothermicity time) and improvesmechanical performance.

These results therefore show that the use of a high-molecular-weightpolyamine makes it possible to accelerate the gelation, while at thesame time maintaining an exothermicity peak distant from this gelation.The addition of various components to the mixture makes it possible tocontrol the gelation and the exothermicity peak, while maintaining orimproving mechanical performance.

Example 3 Bonding of Hot-Dipped Galvanized Steel to Itself

Measurement of the shear strength according to the protocol of the ISO4587 standard (galvanized steel test pieces).

Components B1 B2 B3 B4 B5 Methyl 28.1 27.4  25.4 26.25 28.25methacrylate 1,4-Naphtho- 0.003  0.003 0.003 0.003 0.003 quinone VTB2000x168 28.0 28.0  28.0 28.0 28.0 Isobornyl 5.5 5.5 5.5 5.5 5.5methacrylate Hydroxyethyl 6.0 6.0 6.0 6.0 6.0 methacrylate Methacrylic4.0 4.0 4.0 4.0 4.0 acid Genorad 40 3.0 3.0 3.0 3.0 3.0 Saccharin — —2.0 2.0 — DMA — 0.9 0.9 — — PTE 1.4 1.2 1.2 1.2 1.2 LCV 0.5 — — 0.050.05 Fillers 23.5 24.0  24.0 24.0 24.0 Shear strength 15.7 1.1 9.3 8.21.5 MPa MPa MPa MPa MPa Fracture 100% 100% 100% 100% 100% surfaces cohe-adhe- adhe- adhe- adhe- sive sive sive sive sive NB: The shear strengthof formulation B1 was performed on aluminum. For B1, gel time (on 20gr): 11 min 52 s. Maximum exothermicity: 14 min 36 s, 104° C. Thegelation time is thus delayed and is close to the maximum exothermicitytime. This adhesive is particularly suitable for uses in the field ofbonding large parts.

Example 4 Bonding of Electrogalvanized Steel to Itself

Measurement of the shear strength according to the protocol of the ISO4587 standard (electrogalvanized steel test pieces).

Components C1 C2 C3 C4 C5 Methyl  49.997  49.997  47.997  47.997  48.797methacrylate 1,4-Naphtho-  0.003  0.003  0.003  0.003  0.003 quinoneKraton D1160 16.0  16.0  16.0  16.0  16.0  Kraton MD6455 5.0 5.0 5.0 5.05.0 VTB 2000x168 7.0 7.0 7.0 7.0 7.0 A2EH 4.0 4.0 4.0 4.0 4.0 HEMA 4.04.0 4.0 4.0 4.0 Genorad 40 2.0 2.0 2.0 2.0 2.0 Methacrylic 4.0 4.0 4.04.0 4.0 acid Saccharin — — 2.0 2.0 2.0 DMPT 0.9 — — 0.9 — DMA — 0.9 0.9— — LCV — — — — 0.1 PTE 0.6 0.6 0.6 0.6 0.6 ClearStrength 4.0 4.0 4.04.0 4.0 303H Disparlon 6500 2.5 2.5 2.5 2.5 2.5 Shear strength 1.3 2.719.1 5.2 18.3 MPa MPa MPa MPa MPa Fracture 100% 100% 100% 100% 100%surfaces adhe- adhe- cohe- adhe- cohe- sive sive sive sive sive

The invention claimed is:
 1. A composition that can be used in astructural adhesive, said structural adhesive being formed from saidcomposition and from a catalyst comprising a radical polymerizationinitiator of peroxide type, said composition comprising: (a) at leastone methacrylate ester monomer, (b) a phosphate-ester-based adhesionpromoter, (c) a cure accelerator comprising a tertiary amine of formula:

said composition further comprising saccharin.
 2. The composition ofclaim 1, further comprising a compound selected from the groupconsisting of isobornyl acrylate (IBXA), 2-hydroxyethyl methacrylate(HEMA), 2-hydroxypropyl methacrylate (HPMA), 2-(perfluorooctyl)ethylacrylate (POA), tetrahydrofurfuryl acrylate (THFA) andisobutoxymethylacrylamide (IBMA).
 3. The composition of claim 1, furthercomprising a mixture of HEMA and HPMA.
 4. The composition of claim 1,wherein said phosphate-ester-based adhesion promoter is methacrylated.5. The composition of claim 4, wherein said phosphate-ester-basedadhesion promoter is the 2-hydroxyethyl methacrylate phosphate ester ora mixture of 2-hydroxyethyl methacrylate monophosphate and diphosphateesters.
 6. The composition of claim 1, further comprising an amine (d)selected from the group consisting of substituted or unsubstitutedtoluidines, anilines and phenols.
 7. The composition of claim 1, furthercomprising a metallic acrylate monomer (e).
 8. The composition of claim1, further comprising at least one elastomer (f).
 9. The composition ofclaim 8, wherein said at least one elastomer (f) is selected from thegroup consisting of functionalized or nonfunctionalized poly-butadiene,polyisoprene, polychloroprene and blends of these components.
 10. Thecomposition of claim 1, further comprising an elastomeric blockcopolymer containing styrene and at least one second monomer (g). 11.The composition of claim 10, wherein said second monomer of theelastomeric block copolymer (g) is selected from the group consisting ofisoprene, butadiene and ethylene.
 12. The composition of claim 10,wherein said elastomeric block copolymer (g) is astyrene-isoprene-styrene (SIS) copolymer, and further comprising atleast one elastomeric block copolymer containing styrene and (butadieneor ethylene) (h).
 13. The composition of claim 12, wherein said at leastone elastomeric block copolymer (h) is selected from the groupconsisting of a styrene-butadiene-styrene (SBS) copolymer and astyrene-isoprene-butadiene-styrene (SIBS) copolymer.
 14. The compositionof claim 1, further comprising particles (i) formed from a thermoplasticshell and from an elastomeric core.
 15. The composition of claim 14,wherein said particles (i) are selected from the group consisting ofacrylonitrile-butadiene-styrene, methacrylate-butadiene-styrene,methacrylate-acrylonitrile-butadiene-styrene andmethacrylate-acrylonitrile particles, and mixtures thereof.
 16. Thecomposition of claim 1, further comprising at least one acrylate estermonomer (j) in which the alcohol part has at least one linear chain ofat least 6 carbon atoms.
 17. The composition of claim 16, wherein saidat least one acrylate ester monomer (j) is a methacrylate or acrylatemonomer.
 18. The composition of claim 16, comprising a mixture of twoacrylate monomers (j).
 19. The composition of claim 1, furthercomprising at least one additional compound selected from the groupconsisting of a rheology modifier and an acid monomer.
 20. Thecomposition of claim 1, wherein said methacrylate ester monomer (a) isselected from the group consisting of methyl methacrylate and ethylmethacrylate.
 21. A method for adhesively bonding one material to asecond material comprising the step of using the composition of claim 1and a catalyst comprising a radical polymerization initiator of peroxidetype to bond one material to a second material.
 22. The method of claim21, wherein at least one material is metallic.